4 speed or 4 speed OD?

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dvboth

dvboth

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I am putting a beefy 360 and maybe a 3.23 rear gear in my duster and was wondering which would be the better way to go as far as transmissions a 4 speed or 4 speed OD?

not a racer more of a cruiser!
 
If it's just a fun cruiser, go with the OD for cruising pleasure and mileage
 
I know the OD is not as strong, but I'm planning to try one behind my 5.9 that will be built to around 400 hp. I'm going with 4.10s. Not such an issue with 3.23s. What will your tire diameter be?
 
Idaho said:
I know the OD is not as strong, but I'm planning to try one behind my 5.9 that will be built to around 400 hp. I'm going with 4.10s. Not such an issue with 3.23s. What will your tire diameter be?
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4:10 may make your first gear almost useless as the o/d has a 3.09 first gear ratio
3:23 would be an awesome gear to run with it
 
I've read the argument that the OD is not as strong, but I have to wonder. Doug Dutra's article on SlantSix.org says otherwise. He clearly says that they are both the same strength. His not an opinion I would consider fly by night, either.
 
an od can be built as stout as the regular one to one four speed with a cast iron case or bushing in the aluminum.

Bigger difference comes in the gear shift width.

The od uses the last gear so the wheels are turning faster than the driveline which saves fuel.

So with that, the OD has a wider gear ratio range with only 3 gears....basically its a three speed with an overdrive last gear.

So that being said, you will notice that if you "get on it" you will have to rev the engine more and hold a gear longer to keep the pull going and it will have a slight hesitation when you get into the new gear.

Not so much a negative but if you go with an OD, don't plan on any competitive situation because it will make a big difference and in extreme competition (track) it will disappoint.

But as a gas sipper .....perfect.....interstate highway, low RPMs, low noise. 70+MPH...... nice.
 
RustyRatRod said:
I've read the argument that the OD is not as strong, but I have to wonder. Doug Dutra's article on SlantSix.org says otherwise. He clearly says that they are both the same strength. His not an opinion I would consider fly by night, either.
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From what I have read I gather that the aluminum case o/d is weak and the cast iron one is much better strength wise but not as tough as a standard 4 speed
 
Keep in mind that lower and lower rear gears means you re-HEALLY need to pay attention to shaft balance, U joint condition and angles. "Memories" LOL of my Jeepin days with some of the guys runnin' 5:38s and OD. Ye.....you can do 70, OK, but that shaft down there is REALLY turnin'
 
74DartSwinger360 said:
From what I have read I gather that the aluminum case o/d is weak and the cast iron one is much better strength wise but not as tough as a standard 4 speed
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yes, but even still the aluminum is still a lot stronger than what is commonly written.

Even I have had the aluminum ones come apart on me but if you drive it normal there wont be a problem.

Best bet if you want anything to last is try not being an ape.......when I had them come apart on me its because I was driving like a she-ape and you cant really blame a part failure that was abused beyond normal.
 
67Dart273 said:
Keep in mind that lower and lower rear gears means you re-HEALLY need to pay attention to shaft balance, U joint condition and angles. "Memories" LOL of my Jeepin days with some of the guys runnin' 5:38s and OD. Ye.....you can do 70, OK, but that shaft down there is REALLY turnin'
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words of wisdom, because the in od the rear wheels are turning faster than the drivetrain which is why OD units have a larger input bearing
 
Every Muncie 4 speed ever built was aluminum, including the M22 "rockcrusher". They can take some serious abuse.
 
In a regular 4 speed the input and output shafts are locked together in fourth (turning the same speed). The power flow is in and out, effectively along the same shaft in 4th gear.

In the 4 speed overdrive, however, third gear is when the input and output are locked, but in fourth, the power all goes through the countershaft so that the output shaft can be "overdriven", and this occurs for extended periods of time, at highway speeds, and under a high power demand. This extra load puts more side thrust on the countershaft, and tends to wear out the countershaft needle bearings and the pin itself. Also, the side load tends to work the pin hole in the aluminum case, and because the input and output are turning a different speed in fourth the needle bearings between the two shafts, and the nose of the output where they ride tend to wear more.


Personally though, I like the overdrive 4 speed and have one that I intend to use in my next build. I love the 3.09 low, and the larger gear spread does not bother me. I think it is an awesome and affordable transmission for the street.
 
RaniDart70 said:
an od can be built as stout as the regular one to one four speed with a cast iron case or bushing in the aluminum.

Bigger difference comes in the gear shift width.

The od uses the last gear so the wheels are turning faster than the driveline which saves fuel.

So with that, the OD has a wider gear ratio range with only 3 gears....basically its a three speed with an overdrive last gear.

So that being said, you will notice that if you "get on it" you will have to rev the engine more and hold a gear longer to keep the pull going and it will have a slight hesitation when you get into the new gear.

Not so much a negative but if you go with an OD, don't plan on any competitive situation because it will make a big difference and in extreme competition (track) it will disappoint.

But as a gas sipper .....perfect.....interstate highway, low RPMs, low noise. 70+MPH...... nice.
Click to expand...

Interesting info Rani. I may well find the OD is not the ticket, but I have it, and have already built up my 4.10 8.8 rear so I'm going to try it out. I'll likely make a trip to the track but just out of curiosity not to compete. There's a chance it might make for a fun ride that lights em up real easy without having to scream on the highway. Either way it should be an interesting experiment. :burnout::burnout:

My car won't see a lot of miles and I suspect the "weaker" OD may survive. It's all just dreaming for the time being as I've had no time for the frog.

d55dave, nice description.

Any ideas on how to build it stronger? Rani you mentioned a bushing.

dvboth, hope you're ok with jumping into your thread. I think the info may help with your decision.
 
Id stick with the 4 sp. I have drive both and the "3+1" OD box is just that: a 3 sp with its wide gears (and no convertor torque multiplier) and an OD that seems to just slow the RPM's down. Seems like you could go faster in 3rd (1:1) than the OD 4th as your motor never hits its power band. The 4sp had the 'correct' gear spread and a solid 1:1 4th. With a 3.31-3.55 rear, it was still a nice cruiser, rare 3.73 (?) a 3.91 was a little tight, and the 4.10 and 4.56 were just off the chart truck gears.
 
67Dart273 said:
Keep in mind that lower and lower rear gears means you re-HEALLY need to pay attention to shaft balance, U joint condition and angles. "Memories" LOL of my Jeepin days with some of the guys runnin' 5:38s and OD. Ye.....you can do 70, OK, but that shaft down there is REALLY turnin'
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Exactly.


My philosophy with overdrive is to run a low rear end gear to keep driveshaft speed minimal to make the rear end and u-joints last longer.

You have to decide if you want to race or cruise. OD will be good for a cruiser, 4 speed for a racer...
 
RaniDart70 said:
an od can be built as stout as the regular one to one four speed with a cast iron case or bushing in the aluminum.

Bigger difference comes in the gear shift width.

The od uses the last gear so the wheels are turning faster than the driveline which saves fuel.

So with that, the OD has a wider gear ratio range with only 3 gears....basically its a three speed with an overdrive last gear.

So that being said, you will notice that if you "get on it" you will have to rev the engine more and hold a gear longer to keep the pull going and it will have a slight hesitation when you get into the new gear.

Not so much a negative but if you go with an OD, don't plan on any competitive situation because it will make a big difference and in extreme competition (track) it will disappoint.

But as a gas sipper .....perfect.....interstate highway, low RPMs, low noise. 70+MPH...... nice.
Click to expand...


Great description, Rani.
 
I have a complete OD unit sitting in my shed, been wanting to put it in my swinger. I really think I would appreciate it much more on those long trips I take !
 
..Or you could fork out the cash and go with a 5 speed. Best of both worlds.
 
Rockerdude said:
..Or you could fork out the cash and go with a 5 speed. Best of both worlds.
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Help me understand what two worlds that is. Since the Mopar OD unit has a 3.09 1st and a .69 OD, it already would seem you have the best of both worlds. Who needs to spend 3K bucks for one more gear?
 
I do not think that 400 HP & Lbs. Of TQ are to much for the 4spd OD trans. Of course, the best line I have read in this thread is also the most true line no matter what part or car your talking about.

Don't drive it like an ape.

Or you get served a banana's! LOL
 
I ran a OD behind a stroked 340 with 410 gears. It was great for gas millage and burn outs. Just don't make the mistake of shifting under power, they wont take it. I broke two of them going from 3rd to 4th. Got great gas millage ,Drove from LR Ark to the nats with 340 6pk,4spOD, 410 gears and got decent gas millage. I would vote go for it.
 
dvboth said:
I am putting a beefy 360 and maybe a 3.23 rear gear in my duster and was wondering which would be the better way to go as far as transmissions a 4 speed or 4 speed OD?

not a racer more of a cruiser!
Click to expand...

One of the main problems with the OD is it was built sloppy, they called it a floating cluster gear? The other is the Aluminum main case, now even more at risk because the countershaft is now loose in the main case bores. Now add ATF for gear lube because you want to reduce friction... If you replace the aluminum main case with a cast iron main case, also replace the OD countershaft with the standard countershaft, and add SAE 90 gear oil, things tighten up pretty nice. As others have said above, it is best to look at the OD as a 3 speed with an overdrive. If you want to race, do it with 3 gears and save the OD for the highway. With a relatively high torque, lower RPM small block the OD should be perfect. With 3.91 gears and a .73 OD your final ratio becomes 2.85. With 3.55 gears and a .73 OD your final ratio becomes 2.59. With 3.23 gears and a .73 OD your final ratio becomes 2.36. For long road trips we used to swap in 2.76 gears without the OD for mpg. I'm running a regular cast iron main case OD in my 66 Formula S with 3.91 gears and it runs pretty sweet. 3.09 x 3.91 = 12.08 torque multiplication in first gear, with a 2.85 final ratio.
 
My 2 cents. I have a demon with a 426 wedge that was backed by the od trans.the car ran mid 12's with no trans problem, I personally like the trans and have no issues. As a matter of fact I just put one behind my stock demon and almost doubled the mileage.
 
What gear ratio and tire size in the Demon with 426?
 
I had a regular 4 speed behind a hot 360 in a 73 Dart Sport...I changed to a OD 4 speed and loved it! Great street power between lights, and highway cruise RPM was noticable.
As for strength, work fine no issues! Drag out the 1 st gear and I would skip 2nd straight to 3rd...lol 2 speed with OD on the Highway! I would do it again...was 3:23 sure grip by the way
 
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